/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.catalina.comet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * The CometEvent interface.
 *
 * @author Filip Hanik
 * @author Remy Maucherat
 */
public interface CometEvent {

	/**
	 * Returns the HttpServletRequest.
	 *
	 * @return HttpServletRequest
	 */
	public HttpServletRequest getHttpServletRequest();

	/**
	 * Returns the HttpServletResponse.
	 *
	 * @return HttpServletResponse
	 */
	public HttpServletResponse getHttpServletResponse();

	/**
	 * Returns the event type.
	 *
	 * @return EventType
	 */
	public EventType getEventType();

	/**
	 * Returns the sub type of this event.
	 *
	 * @return EventSubType
	 */
	public EventSubType getEventSubType();

	/**
	 * Ends the Comet session. This signals to the container that
	 * the container wants to end the comet session. This will send back to the
	 * client a notice that the server has no more data to send as part of this
	 * request. The servlet should perform any needed cleanup as if it had received
	 * an END or ERROR event.
	 *
	 * @throws IOException if an IO exception occurs
	 */
	public void close() throws IOException;

	/**
	 * Sets the timeout for this Comet connection. Please NOTE, that the implementation
	 * of a per connection timeout is OPTIONAL and MAY NOT be implemented.<br/>
	 * This method sets the timeout in milliseconds of idle time on the connection.
	 * The timeout is reset every time data is received from the connection or data is flushed
	 * using <code>response.flushBuffer()</code>. If a timeout occurs, the
	 * <code>error(HttpServletRequest, HttpServletResponse)</code> method is invoked. The
	 * web application SHOULD NOT attempt to reuse the request and response objects after a timeout
	 * as the <code>error(HttpServletRequest, HttpServletResponse)</code> method indicates.<br/>
	 * This method should not be called asynchronously, as that will have no effect.
	 *
	 * @param timeout The timeout in milliseconds for this connection, must be a positive value, larger than 0
	 * @throws IOException                   An IOException may be thrown to indicate an IO error,
	 *                                       or that the EOF has been reached on the connection
	 * @throws ServletException              An exception has occurred, as specified by the root
	 *                                       cause
	 * @throws UnsupportedOperationException if per connection timeout is not supported, either at all or at this phase
	 *                                       of the invocation.
	 */
	public void setTimeout(int timeout)
			throws IOException, ServletException, UnsupportedOperationException;

	/**
	 * Enumeration describing the major events that the container can invoke
	 * the CometProcessors event() method with.<br>
	 * BEGIN - will be called at the beginning
	 * of the processing of the connection. It can be used to initialize any relevant
	 * fields using the request and response objects. Between the end of the processing
	 * of this event, and the beginning of the processing of the end or error events,
	 * it is possible to use the response object to write data on the open connection.
	 * Note that the response object and dependent OutputStream and Writer are still
	 * not synchronized, so when they are accessed by multiple threads,
	 * synchronization is mandatory. After processing the initial event, the request
	 * is considered to be committed.<br>
	 * READ - This indicates that input data is available, and that one read can be made
	 * without blocking. The available and ready methods of the InputStream or
	 * Reader may be used to determine if there is a risk of blocking: the servlet
	 * should read while data is reported available. When encountering a read error,
	 * the servlet should report it by propagating the exception properly. Throwing
	 * an exception will cause the error event to be invoked, and the connection
	 * will be closed.
	 * Alternately, it is also possible to catch any exception, perform clean up
	 * on any data structure the servlet may be using, and using the close method
	 * of the event. It is not allowed to attempt reading data from the request
	 * object outside of the execution of this method.<br>
	 * END - End may be called to end the processing of the request. Fields that have
	 * been initialized in the begin method should be reset. After this event has
	 * been processed, the request and response objects, as well as all their dependent
	 * objects will be recycled and used to process other requests. End will also be
	 * called when data is available and the end of file is reached on the request input
	 * (this usually indicates the client has pipelined a request).<br>
	 * ERROR - Error will be called by the container in the case where an IO exception
	 * or a similar unrecoverable error occurs on the connection. Fields that have
	 * been initialized in the begin method should be reset. After this event has
	 * been processed, the request and response objects, as well as all their dependent
	 * objects will be recycled and used to process other requests.
	 */
	public enum EventType {
		BEGIN, READ, END, ERROR
	}

	/**
	 * Event details.<br>
	 * TIMEOUT - the connection timed out (sub type of ERROR); note that this ERROR type is not fatal, and
	 * the connection will not be closed unless the servlet uses the close method of the event<br>
	 * CLIENT_DISCONNECT - the client connection was closed (sub type of ERROR)<br>
	 * IOEXCEPTION - an IO exception occurred, such as invalid content, for example, an invalid chunk block (sub type of ERROR)<br>
	 * WEBAPP_RELOAD - the webapplication is being reloaded (sub type of END)<br>
	 * SERVER_SHUTDOWN - the server is shutting down (sub type of END)<br>
	 * SESSION_END - the servlet ended the session (sub type of END)
	 */
	public enum EventSubType {
		TIMEOUT, CLIENT_DISCONNECT, IOEXCEPTION, WEBAPP_RELOAD, SERVER_SHUTDOWN, SESSION_END
	}

}
